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mem: Warn once if /proc/self/pagemap is unreadable

PATCH Applied Simon Kagstrom 2 participants 2 messages Jun 24, 2015 – Jul 10, 2015

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Simon Kagstrom

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PATCH v2 1/1 mem: Warn once if /proc/self/pagemap is unreadable

Newer kernels make this unreadable for security reasons for non-roots. Running the application will then fill the logs with

rte_mem_virt2phy: cannot open /proc/self/pagemap

messages.

However, there are cases when DPDK is and should be run as non-root, without the need for virtual-to-physical address translations: a typical example is when working with PCAP input/output. This patch adds a start-time check for /proc/self/pagemap readability, and directly returns an error code from rte_mem_virt2phy().

This way, there is only a one-time warning at startup instead of constant warnings all the time.

Signed-off-by Simon Kagstrom <[email protected]>
Signed-off-by Johan Faltstrom <[email protected]>

---
ChangeLog:

v2: Fix use with huge pages.

 lib/librte_eal/linuxapp/eal/eal_memory.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
lib/librte_eal/linuxapp/eal/eal_memory.c +25 -0
index 9b8d946..f4a1936 100644
@@ -111,6 +111,8 @@
 
 static uint64_t baseaddr_offset;
 
+static unsigned proc_pagemap_readable;
+
 #define RANDOMIZE_VA_SPACE_FILE "/proc/sys/kernel/randomize_va_space"
 
 /* Lock page in physical memory and prevent from swapping. */

@@ -135,6 +137,10 @@ rte_mem_virt2phy(const void *virtaddr)
 	int page_size;
 	off_t offset;
 
+	/* Cannot parse /proc/self/pagemap, no need to log errors everywhere */
+	if (!proc_pagemap_readable)
+		return RTE_BAD_PHYS_ADDR;
+
 	/* standard page size */
 	page_size = getpagesize();
 

@@ -1546,12 +1552,31 @@ rte_eal_memdevice_init(void)
 	return 0;
 }
 
+static int
+test_proc_pagemap_readable(void)
+{
+	int fd = open("/proc/self/pagemap", O_RDONLY);
+
+	if (fd < 0)
+		return 0;
+	/* Is readable */
+	close(fd);
+
+	return 1;
+}
 
 /* init memory subsystem */
 int
 rte_eal_memory_init(void)
 {
 	RTE_LOG(INFO, EAL, "Setting up memory...\n");
+
+	proc_pagemap_readable = test_proc_pagemap_readable();
+	if (!proc_pagemap_readable)
+		RTE_LOG(ERR, EAL,
+		        "Cannot open /proc/self/pagemap: %s. virt2phys address translation will not work\n",
+			strerror(errno));
+
 	const int retval = rte_eal_process_type() == RTE_PROC_PRIMARY ?
 			rte_eal_hugepage_init() :
 			rte_eal_hugepage_attach();
Signature · 1 line
1.9.1
Applied
#1 lore raw

2015-06-24 10:33, Simon Kagstrom:

Quoted 13 lines

Newer kernels make this unreadable for security reasons for non-roots. Running the application will then fill the logs with

rte_mem_virt2phy: cannot open /proc/self/pagemap

messages.

However, there are cases when DPDK is and should be run as non-root, without the need for virtual-to-physical address translations: a typical example is when working with PCAP input/output. This patch adds a start-time check for /proc/self/pagemap readability, and directly returns an error code from rte_mem_virt2phy().

Quoted 5 lines

This way, there is only a one-time warning at startup instead of constant warnings all the time.

Signed-off-by Simon Kagstrom <[email protected]>
Signed-off-by Johan Faltstrom <[email protected]>

Applied, thanks